Planta

, Volume 214, Issue 2, pp 288–294 | Cite as

Deoxypodophyllotoxin 6-hydroxylase, a cytochrome P450 monooxygenase from cell cultures of Linum flavum involved in the biosynthesis of cytotoxic lignans

  • Grietje Molog
  • Ursula Empt
  • Stephan Kuhlmann
  • Wim van Uden
  • Niesko Pras
  • August Alfermann
  • Maike Petersen
Original Article

Abstract.

Cell-suspension cultures of Linum flavum L. (Linaceae) synthesize and accumulate aryltetrahydronaphthalene lignans with 6-methoxypodophyllotoxin as the main component. The experimental data indicate that the biosynthesis of 6-methoxypodophyllotoxin occurs via deoxypodophyllotoxin, β-peltatin, and β-peltatin-A methyl ether. The enzyme catalyzing the introduction of the hydroxyl group in position 6 is deoxypodophyllotoxin 6-hydroxylase (DOP6H). The enzyme was shown to be a cytochrome P450-dependent monooxygenase by blue-light reversion of carbon monoxide inhibition and inhibition by cytochrome c. DOP6H is a membrane-bound microsomal enzyme with a pH optimum of 7.6 and a temperature optimum of 26 °C. Deoxypodophyllotoxin is specifically accepted with an apparent Km of 20 µM and a saturation concentration of 200 µM; 4′-demethyldeoxypodophyllotoxin is the only other tested substrate accepted for hydroxylation. DOP6H predominantly accepts NADPH as electron donor; NADH can only sustain low hydroxylation activities. A synergistic effect of NADPH and NADH is not observed. The enzyme is saturated around 250 µM NADPH; the apparent Km for this substrate is 36 µM.

Cell culture (Linum) Cytochrome P450 Lignan Linum (lignan biosynthesis) Podophyllotoxin 

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Copyright information

© Springer-Verlag 2001

Authors and Affiliations

  • Grietje Molog
    • 2
  • Ursula Empt
    • 3
  • Stephan Kuhlmann
    • 1
  • Wim van Uden
    • 2
  • Niesko Pras
    • 2
  • August Alfermann
    • 3
  • Maike Petersen
    • 1
  1. 1.Institut für Pharmazeutische Biologie, Philipps-Universität Marburg, Deutschhausstr. 17 A, 35037 Marburg, Germany
  2. 2.Department of Pharmaceutical Biology, University Centre for Pharmacy, Groningen Research Institute of Pharmacy (GRIP), University of Groningen, A. Deusinglaan 1, 9713 AV Groningen, The Netherlands
  3. 3.Institut für Entwicklungs- und Molekularbiologie der Pflanzen, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225 Düsseldorf, Germany

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